Omicron-adapted COVID-19 vaccines: Could updated shots prevent a fall wave?

Click to play video: 'Health Matters: UK approves double-barreled COVID-19 vaccine'
Health Matters: UK approves double-barreled COVID-19 vaccine
WATCH: Health Matters — U.K. approves double-barrelled COVID-19 vaccine – Aug 16, 2022

The COVID-19 pandemic has a new line of defence – in the form of updated vaccines after the world’s first bivalent shots were approved in the U.K. this week.

A bivalent vaccine targets two different variants of the same virus.

The new vaccines are still awaiting approval in Canada and while there is no word on when that will land, Canadian doctors are optimistic about a potential rollout.

“These updated vaccines are a phenomenal tool, but the real game-changer will be distribution,” said Dr. Omar Khan, a professor of biomedical engineering and immunology at the University of Toronto.

“As long as we can get this out to as many people across the world, this is really what’s going to slow down viral evolution and prevent a new variant,” he told Global News.

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On Monday, the United Kingdom became the first country to approve the so-called bivalent vaccine by Moderna as a booster for adults.

Both Pfizer and Moderna have submitted to Health Canada applications for bivalent vaccines targeting the original variant of the virus and the Omicron BA.1 sublineage.

Those submissions are currently under review, Mark Johnson, a spokesperson for Health Canada, told Global News on Monday.

“As with all COVID-19 vaccine submissions, these are being reviewed on a priority basis by dedicated scientific teams,” he said in an email.

Click to play video: 'Who should take the second booster shot?'
Who should take the second booster shot?

In Canada, daily COVID-19 cases are on the decline, but public health officials and other experts have warned infections could surge again in the fall as activities move indoors.

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That is why the National Advisory Committee on Immunization (NACI) has recommended booster shots this fall in advance of a possible future wave of COVID-19.

Will updated vaccines protect against new variants?

Currently, the adult population can get boosted with COVID-19 doses that target the original variant of the virus.

The bivalent vaccines have been updated to include the Omicron BA.1 subvariant – but not BA.5, which is currently dominant in Canada and globally.

Because of that, Dr. Jun Liu, an infectious disease expert at the University of Toronto and researcher for the COVID-19 Immunity Task Force, is not certain the new vaccines will have a considerable impact in preventing a fall wave.

“Ideally, I think having the BA.5 variant to be included would be the best to counter any of the immediate wave in the fall,” he said.

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Nearly half the total Canadian population has been boosted with a third dose and roughly 10 per cent have received a fourth shot.

The U.S. Food and Drug Administration has recommended COVID-19 vaccine manufacturers change the design of their booster shots to include components tailored to combat the BA.4 and BA.5 subvariants of Omicron.

Even though mRNA vaccines are easy to update, the challenge is testing them in clinical trials to show safety and efficacy, which takes more time, experts say.

It’s a “catch-up game” as the virus is changing very rapidly, said Liu.

“We’re basically racing against the virus, and unfortunately, we’re always falling behind.”

Click to play video: 'Omicron subvariants fuel fears about COVID-19 reinfections'
Omicron subvariants fuel fears about COVID-19 reinfections

In approving Moderna’s bivalent vaccine, the U.K. medicines regulator said its decision was based on clinical trial data that showed the booster triggered “a strong immune response” against both Omicron (BA.1) and the original 2020 virus.

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The Medicines and Healthcare products Regulatory Agency also cited an exploratory analysis in which the shot was found to generate a good immune response against Omicron offshoots BA.4 and BA.5.

No serious safety concerns were identified with this new formulation, the agency added.

Based on clinical trial data, Pfizer said in June that its Omicron-adapted bivalent vaccine elicited substantially higher neutralizing antibody responses against Omicron BA.1 when compared with the current COVID-19 vaccine.

Preliminary laboratory studies demonstrate the updated vaccine also neutralized BA.4 and BA.5 subvariants but to a lesser extent, Pfizer said.

Khan is hopeful the updated vaccines will offer protection against reinfection.

“Just like how the original version of the vaccine was future-proof up until Delta and even to some extent Omicron, we should hopefully see the same level of perseverance in these vaccines,” he said.

— with files from Reuters

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